Indicator



June 13, 1939. L. E. DODGE 2, 1

INDICATOR Filed June 2'7, 1936 @bf-s. 1. Q

Patented June 13, 1939 UNITED STATES PATENT OFFICE INDICATOR Lyman E. Dodge, Morris Township,

Morris County, N. J., assignor to Frank G. La Mar,

This invention relates to electrical fuse devices, especially to integrity indicator means for cartridge type fuses, and more particularly to the class of such integrity indicators in which the indicator device is formed as a unitary structure having an entity distinct from that of the cartridge fuse or other type of fuse with which the indicator device is intended to be assembled in use.

Among the requirements which are desirably to be satisfied by a fuse integrity indicator intended for assembly with a cartridge type fuse, and to provide for which is an object of the present invention, is the requirement that it shall be readily capable of attachment to the fuse cartridge, or to the spaced-apart electrical terminals by which the fuse is contacted and held and there by included in the circuit to be protected; also that such an integrity indicator shall be adaptable for 20 use with cartridge fuses of generally standard sizes and type, though differing in non-essential details; also that the adaptation to a given type of fuse can be effected without alteration of the structure of the fuse cartridge by a user, and that if any alteration of fuse cartridges, or of the integrity indicator shall be required of the manufacturer, in its adaptation to one or another make of fuse, such alteration shall be of an inconsiderable character, and may be performed at the manufactory instead of at the place of installation of the cartridge fuse and indicator.

A further requirement is to have the integrity indicator so conjoined with the fuse cartridge structure in use that it will not be displaced by the vibrations and shocks encountered ordinarily in the use of such fuses and their cooperating integrity indicators; also that the integrity indicator shall be so disposed with relation to the fuse that its presence will not interfere unduly with manipulation of the fuse cartridge during inspection, adjustments or renewals thereof.

Many of the integrity indicators at present applied to cartridge fuse installations for the aforesaid purpose, fail to satisfy the foregoing requirements in many respects and none of such indicators is to be regarded as meeting all of the requirements in a completely satisfactory manner.

Among the outstanding deficiencies that have been characteristic of fuse integrity indicators, may be mentioned their tendency to shake off and fall into positions where they cause dangerous shorts, or crosses, in the electrical circuits sought to be protected by the fuse, and the integrity or condition of which is desirable to be indicated; also the tendency to become loose to such 1936, Serial No. 87,642

an extent that the electrical contact is impaired, or broken, even if the indicator is apparently in place, a condition which is dangerous for the reason that a defective circuit condition may exist without being signalled, the normal appearance of the indicator being deceptive.

Other objects and advantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses, and the novel features will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiments selected to illustrate the invention, reference will be had to the accompanying drawing and the several views thereon in which like characters of reference designate like parts throughout the several views, and in which:

Figure 1 is a view in vertical longitudinal section of a protective device for electrical circuits in which a fuse cartridge element is shown in assembly with a support and with an integrity indicator element; Fig. 2 is a plan view thereof; Fig. 3 is a view in vertical section on the line 33 of Fig. 1, the view being taken in the direction indicated by the arrows at the end of the line; Fig. 4 is a detail view in perspective of the integrity indicator element taken separately.

In a now preferred embodiment of the present invention selected for illustration and description, the member designated generally by the reference character F is an electrical fuse of the cartridge type, the part II being a barrel or cylindrical body of insulating material confining the fusible element 12, which according to conventional usage has suitable electrical connections (not shown) with metal terminal caps l3 and I4 screwed upon threaded ferrules l5. In the instance illustrated the cartridge F is held in opera.- tive position by metal clips of known form, the feet l6 thereof being spaced apart and respectively secured to a block I! of insulating material by screws I8, the heads [9 of which are set against shoulders 20 of recesses 2| which are sealed with a suitable plastic 22. These screws may be desirably, as shown, tapped into straps 23, 24 furnished with binding screws 25, 26 which constitute the terminals by which the protective device as an entity is connected into the electrical circuit to be protected.

The structure above identified is of convena tional type, and intended to be merely illustrative, it being understood that upright spring members 21 and 28, extending upward from the feet I6, as shown in Fig. 3, embrace, and serve to retain yieldingly, the metal caps l3 and I4, making good mechanical and electrical connection therewith, so that a stout pull is required to remove the fuse plug F from its clipped position shown, in which its contained fuse element |2 operates normally to protect the circuit in known manner.

In order to afford a desirable visual and attention-arresting indication of the fusing of element |2 by passage therethrough of an electrical current of predetermined strength, provision is made, pursuant to the present invention, of an indicating device designated generally by the reference character I, and which is mounted upon the cartridge F by means of a pair of spaced eye clips or members 3| and 32 of annular form and each having a radial exterior projection 29 for connection with the indicator proper, and a prong-like interior offset 30 adapted to enter into retentive engagement with the periphery of the fuse cartridge barrel II when assembled therewith in the manner now to be described.

The eye clips 3| and 32 are desirably of identical structure in general respects and the exterior lug or projection 29 of each is designed to afford a sturdy support for the associated end of an elongated body member 33 of the indicator device, it being understood that the indicator device herein shown and described is merely an illustrative example of numerous such integrity indicators which may be substituted at will in the protective assembly embodying the present invention.

The connection between the barrel 33 of the indicator device and its end supporting eye clips 3| and 32 is effected, in the instance shown, by means of metal bushings 34 and 35, one for each end of the barrel, within which the bushings are fitted snugly, being preferably held therein positively, as by the use of self-driving screws 36 or other suitable devices. The cup-shaped bushings 34 and 35 are preferably secured metalically to the projections 29 of the eye clips 3| and 32, as by sweating, brazing or soldering, and the lower wall of the barrel is desirably recessed, as at 31, so that room is left for insertion of a disc 38 of insulating material at each end, held in place by a fastener 39, such as a self-driving screw.

The indicator proper may conveniently take the form of a neon-filled discharge lamp N, with exterior terminals 4| and 42, the first of which terminals is soldered to the adjacent lug 29 of eye-clip 32 while the latter terminal 42 is connected to one end of a resistance R of the order of 50,000 to 100,000 ohms and from the other end of which a conductor 43 leads to the lug 29 of the eye-clip 3|.

The integrity indicator proper above described as one illustrative form suitable for use in this protective assembly forms the subject of a more complete description and claims in copending application for Letters Patent Serial No. 21,950, filed by Frank C. La Mar, May 17, 1935, the present invention having for an outstanding object the provision of improved attaching means therefor and for other indicators with which such attachment means may be utilized advantageously.

The attaching clips 3| and 32 are preferably so spaced that when assembled upon the cartridge barrel II, as shown in Fig. 1, the latter slips easily into the central openings 40, (see Fig. 3), but each eye-clip is so engaged by a suitable metal portion of the cartridge structure, such as the contiguous screw cap l3 or 4, that the rings 3| and 32 are thereby cramped against the periphery of the insulating barrel II as shown clearly in Figs. 1 and 3 and the prongs 30 are driven into the material thereof.

Such action creates not only a strong mechanical union between the integrity indicator structure, as an entity, and the barrel of the fuse cartridge, so that the integrity indicator is fixed against displacement either lengthwise or rotatively thereupon, but an excellent electrical connection is promoted by the rubbing metal-tometal engagement between the rings 3|, 32 and the screw caps l3 and M, respectively, and as long as the integrity indicator is allowed to remain upon the fuse cartridge it will be included in a shunt circuit of the working circuit protected by the fuse F.

As long as the fusible element l2 of the cartridge remains intact, the current will find an easier path through |2 than through the lamp N, by reason of the high resistance R in series with the lamp, but the latter will be energized whenever sufficient current is diverted therethrough by fusion of the fusible element |2; whereupon a visible and attention-resting indication of the impaired circuit condition will be yielded by the characteristic neon glow, visible through the window 44.

The integrity indicator I above described does not interfere in the least, however, with the manipulation of the fuse cartridge F, but may be considered as of assistance in removal of the latter, serving as a puller in known fashion.

After removal of the fuse cartridge, with the integrity indicator still in place thereon, the screw cap l3 or the screw cap M, or both, may be removed while the integrity indicator is re-- tained in place by frictional contact, so that it need not be disturbed in the ordinary course of inspection, adjustments and replacements incidental to use of such protective devices, however, if at any time it is desired to separate the fuse cartridge and its integrity indicator, the latter may be slipped from the barrel H by s1icling the eye clips 3|, 32 along the same readily.

In the form already disclosed no alteration, or special structure of the conventional cartridge fuse structure is required, but on the contrary the integrity indicator can be provided in stock sizes corresponding to standard sizes of use cartridges of numerous makes, with considerable tolerance for variations in non-essential details, so long as the fuse cartridges suitable to interfit with the usual arms 2'! and 28 of the supporting clips.

Although I have particularly described one particular physical embodiment of my invention and explained the operation, construction and principle thereof, nevertheless, I desire to have it understood that the form selected is merely illustrative, but does not exhaust the possible physical embodiments of. the idea of means underlying my invention.

\Vhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an integrity indicator device for a cartridge fuse, an elongated body, an indicating means carried by said body, and a pair of ringshaped eye clips or contact terminals connected electrically with said indicating means and ex tending from said body into position to fit respectively over the barrel of the fuse cartridge, having central openings of less diameter than that of the metal caps on said cartridge barrel, said ring-shaped eye clips being disposed at a distance from each other sufficiently in excess of the distance between said metal caps to cause said ring-shaped eye clips to be canted into engagement with said barrel when said end caps are screwed home upon the cartridge barrel.

2. A protective device comprising the elements combined and cooperating as set forth in claim 1, and further characterized by having said ringshaped contact terminals adapted to enter into firm electrical contact with a metal end part of said fuse, and formed with exterior lugs affixed to said indicator body.

3. A protective device comprising the elements combined and cooperating as set forth in claim 1, and further characterized by having said ringshaped contact terminals formed as sheet metal parts provided with exterior lugs affixed to said indicator body, each ring-shaped contact terminal having at least one interior prong adapted to penetrate retentively into the cartridge barrel,

4. A protective device comprising the elements combined and cooperating as set forth in claim 1, and further characterized by having said ring shaped contact terminals formed as sheet metal parts formed with exterior lugs aflixed to said indicator body, each of said ring shaped parts having a prong adapted to engage sharply a portion of the underlying cartridge structure, the prongs on opposite rings being turned toward each other, so that as the ring shaped parts are canted toward each other the prongs will enter the cartridge in opposite directions.

LYMAN E. DODGE. 

